A single cartridge can charge a single cell phone twice (or charge two cell phones once), via USB. But the methanol cartridges cost $35 for a five-pack. Charging a phone from the grid is still probably cheaper, and as more renewable energy sources come online, it could be just as environmentally sound—especially considering all the waste left over from used-up methanol cartridges.

For now, at least, the Dynario is only available in Japan in a limited run of 3,000 units. If sales go well, the device will most likely show up in stores around the world. But if solar cell-phone chargers continue to improve and gain popularity, don't be surprised if fuel-cell chargers stay firmly planted in the background. After all, solar chargers don't need to be supplemented every so often with expensive cartridges.